When a solid body moves at supersonic speed through the atmosphere a shock wave is created immediately in front of the body. Many supersonic bodies have a pointed nose configuration that helps reduce atmospheric drag. In such a case there is only a very small area in front of the supersonic body having a detached normal shock wave, i.e., one normal to the direction of motion of the vehicle. The developed shock wave is essentially an oblique wave attached for practical purposes to the point of the nose portion. There is only a relatively small pressure rise behind the oblique wave, resulting in a significantly reduced drag on the body. In essence, supersonic bodies having noses with small divergence angles do not have a substantial stagnation zone, as would otherwise occur behind a substantial normal shock wave directly in front of the vehicle.
As the speed of the TAV or projectile becomes considerably higher than Mach 1, problems of aerodynamic drag and heating become commensurately more serious. This is because the strength of the shock waves generated by motion of the body depends on Mach number; the higher the Mach number the higher is the pressure of the atmosphere directly behind the shock waves and essentially adjacent to the nose portion of the body.
Numerous solutions have been proposed for reducing the aerodynamic drag and the heat generation in front of supersonic bodies, with each solution focusing on a particular benefit. Ross et al, U.S. Pat. No. 3,259,065, discloses a high-velocity forwardly directed flow of cooled air projected at supersonic velocity directly in front of a blunt leading portion of the body to form a jet or virtual spike. This virtual spike extends forward into the oncoming supersonic air stream until it terminates at a point forward of the body where a shock wave commences due to interaction between the cooled jet air flow and the oncoming atmosphere. Behind this shock wave, a subsonic boundary layer on the virtual spike forms a conical trapped air region. Consequently, the air flow around the body is substantially identical to that which would have been produced by a conventional elongated nose cone or probe. Among the benefits thus obtained are: (1) the substantial elimination of a high temperature zone directly in front of the vehicle nose, where it is most advantageous to locate infrared or similar sensor devices, and (2) a certain degree of control over the aerodynamic drag by varying the amount and angle of attack of cool air flowing from the vehicle.
Taylor et al, U.S. Pat. No. 4,650,139, discloses a solid aerospike attached, for example, to the nose of an asymmetrical space vehicle, e.g., a vehicle which carries the space shuttle. The aerospike alters the aerodynamic effect on the entire vehicle during supersonic space flight through the atmosphere. The aerospike basically comprises a tapered elongated tubular element having a first end attached to the space vehicle nose and a second or free end terminating in a substantially rounded disk-like tip member, as illustrated in FIG. 7 of this reference. The aerospike can be either flexible or rigid and may include means for emitting a fluid, e.g., a gas or a liquid, from the tip member to enhance aerodynamic flow. The presence of the disk-like free end of the aerospike, possibly coupled with the flow of a fluid therefrom, inter alia, serves to retard or eliminate reattachment of shock waves that would otherwise be generated by supersonic motion of the space vehicle. The distance the aerospike is projected forward of the vehicle and the flow rate of the fluid emitted from the forward end thereof are controlled parameters.
Although both Ross et al and Taylor et al disclose controlling the flow rate of a fluid to a region ahead of the forwardmost portions of a supersonic body, neither is concerned with reducing the atmospheric mass density in front of the body by ejecting a mass of material forwardly from the body wherein the ejected material reacts with material in the atmosphere to provide the desirable reduction in atmospheric mass density to reduce drag and heating of the body.
Schoppe, U.S. Pat. No. 3,620,484, on the other hand, discloses reducing the strength of the shock wave and the consequential fluid drag on a supersonic vehicle, by using a small diameter gas tube or pipe protruding from the front of the body so that the forwardmost portion or nose of this gas tube generates relatively small normal shock waves. If a gas is emitted from the tube, the head end of the main body (which is further downstream from the gas-emitting free end of the gas tube) generates an additional strong shock wave in conventional manner. It is believed that this maintains the air flow around the nose of the supersonic vehicle body and may eliminate the sonic boom which normally accompanies the presence of such shock waves. In Schoppe, the supersonic body has a blunt nose and means for applying heat to the zone immediately in front of and surrounding the nose surface so that there is substantial nose shock wave reduction while heat is being applied. There is a controlled flow of fuel laterally of the forwardly extended spike, at a point closer to the end where the spike is attached to the blunt main supersonic vehicle body than to the front of the gas tube. Burning fuel in the high compression zone defined by the relatively weak shock wave attached to the front end of the gas tube, to provide controlled amounts of heat at selected locations in front of the main blunt supersonic vehicle body significantly reduces the strength of the shock waves that otherwise would be generated by the body. This reduces the aerodynamic drag and, by a carefully controlled unsymmetrical application of added heat, selective use of perpendicular forces on the supersonic vehicle can be used to control its flight.
In the above-discussed prior art, a fluid flows from the body, directed either forwardly or laterally of the line of motion of the body. In none of the discussed references is there a flow of material provided from the supersonic body to form immediately in front of the supersonic body a low mass density atmosphere of a large enough transverse cross-section to receive the entire supersonic body.
Various generalized suggestions have been made within the relevant field of art for employing lasers to reduce atmospheric pressure by projecting laser beams; however, no specific or concrete proposals for suitable apparatus or method to accomplish this are presently known.